Elastic-fluid turbine



Oct. 14, 1941. w R, NEW 2,258,793

ELAsTIc-FLUID TURBINE Filed March 19, 1940 4 SheeS-Shee'f. 2

wlNEssEs; Fr, Q 6. INVENTOR BY al, BIM

' ATTORNEY 95E/Wk 774W. WlNsToN R. New. 6. H

355 i, Flcp FGQS. I

Oct. 14, 1941. w, R, NEW 2,258,793

ELAsTIc-FLUID TURBINE Filed March 19, 1940 4 Shees-She'et Av L',

T X .33 gnu; o

BY Rf, @Aanv-1n ATroRNEY WlNsToN R. New.

Patented Oct. 14, 1941 UNITED siy T E S .531.

or to Westinghouse Electric er Manuliactg Company, East Pittsburgh, Pa.,a corporation of Pennsylvania.

Application March 19, 1940, Serial No. 324,743

l1 Claims.

My invention relates to elastic-fluid turbines and it has for an objectto provide apparatus of this character having blading particularlysuitable for the fluid velocities to be encountered in order to secureimproved performance.

I have found that turbine blades or vanes having sharp inlet edgesshould be used with elastic iluld entering at super-acoustic velocitiesand that blades or vanes having well-rounded inlet edges should beemployed with elastic fluid entering at sub-acoustic velocities. Aturbine blade or vane must always be capable of functioning over a rangeof directions of the approaching stream. If the approaching stream has asubacoustic velocity, then blades -or vanes of foil section havingwell-rounded inlet edges facili- 'tate orderly transport of fluid aroundtheir boundaries by propagating pressure disturbances into theapproaching stream in such a way as to introduce changes in thedirection and magnitude of velocity of elementary filaments before theyare arrested by the solid surfaces, therebycausing the stream toaccommodate itself to the blades or vanes over a wide angle of approach.A sharp inlet edge or lip produces pronounced deviation from thestreamlined shape having a wellrounded inlet edge and makes a vane orblade selective in its response to various velocity directions but doesnot reduce its drag. Therefore, at sub-acoustic entering velocities,since a sharp inlet'edge gives no compensation for the loss of theadvantage of a foil with a well-rounded inlet edge to deal with theelastic iiuid over a wide ,range of angle -of approach, blades or vanesof foil section having well-rounded inlet edges should be used.'

The possibility of affecting the velocity field upstream by means ofpressure disturbances propagated from the blades or vanes disappearswhen the elastic fluid approaches at super-acoustic velocities. Thephenomenon of compression shock ispeculiar to the super-acoustic caseand it causes energy losses proportional, among other factors, to theprojected areal of the leading edge of the blade or vane in thedirectionl of the approaching stream, and it is, therefore, desirable tominimize such projected area by providing a lip or thin leading edge inorder to reduce energy losses due to compression shock.

The function .of a turbine nozzle or blade ele` ment is to derive from achange in momentum of the motive iiuid, a force which is normal to thefor any. sulciently smallelement of time, the existence of a torquerests'upon continuous generation and absorption of momentum through themechanism of continuous time change in the p vector representingvelocity. Since fundamentally all turbine blades or vanes abstractenergyv exists a velocity, uniquely definable in terms of conditions ofstate (sealer quantities) at which a pressure wave travels in the mediumat those state conditions, and this velocity is the acoustic velocity.If the fluid velocity is sub-acoustic, as is usually the case with allof the blades or vanes of a conventional turbine except possibly thoseof the first moving row of the impulse stage, and particularly if theangle of approach to the blades or vanes varies, in consequence ofvariation in load or speed or both, then blades or vanes of foil sectionhaving well-rounded inlet edges should be used because the pressuredisturbances set up by such inlet edges causes the element andtangential toits supporting member. With a governor valve metering thequanapproaching stream to better accommodate itself to the blades orvanes over a wide range of variation in the angle of approach of thefluid.'

If the entering velocity is super-acoustic, asfis frequently the casewith the first row of moving blades of` the initialmultiple-velocity-abstrac tion stage, not only would it be impossiblefor rounded .inlet edges of the blades to propagate pressuredisturbances against the stream causing the approaching uid to betteraccommodate itselfto the ,blades or vanes, but, on account of shock,such edges would present excessive projected or impact area to thestream and consequently involve excessive shock losses. Therefore, withsuper-acoustic inlet velocity, the blades or vanes should present aminimum projected area to the approaching stream, that is, they shouldhave thin or sharp leading edges.

The' present invention is also concerned with certain aspects ofsingle-velocity-abstraction stages for use with substantiallysub-acoustic velocities. Such stages may be either symmetrical oranti-symmetrical as regards the enthalpy change across the stationaryand moving blade or vane elements. In a steam turbine stage in Y whichkinetic energy is generated principally in a stationary nozzle andvelocity abstraction occurs in one moving row, that is, ananti-symmetrical stage, sub-acoustic velocities are almost invariablyencountered. Heretofore, turbine designers have distinguished between animpulse or Rateau stage and a reaction or Parsons stage from the pointof view of geometry of blade shapes without taking into considerationthat they were dealing with sub-acoustic velocities and that the onlyreal distinction to be made was on the ground of symmetry or lack ofsymmetry with respect to distribution of enthalpy change over thestationary and moving blades of a stage. They did not realize that bladeor vane elements encountering sub-'acoustic velocity flow should eachconsist of a streamlined foil with a wellrounded inlet or leading edge.,The crescent;- type blade commonly employed in anti-symmetrical stagesis a pronounced deviat-ion from the streamlined shape and it isselective in its response to various inlet velocity directions, at whichall stages must operate, without compensation for loss of flexibilitythrough decreased drag.

While impulse action in a. turbine stage involves abstraction, by themoving blades, of velocity energy already generated in the stationaryblade or nozzle passages and reaction action involves transformation ofheat'energy of elastic fluid into velocity energy appearing both asvelocity of the moving blades and of elastic uid discharged from thelatter, the usual impulse stage involves some reaction and reactionstages involve some impulse. While the transformation of velocity energyis eicient so long as the inlet edges are at an angle correct for theangle of approach of the elastic fluid and the turning angle thereof isequal to that required' by the elastic uid at the design operatingconditions, departures of the angle of approach from that correct forthe inlet angle result in less eilicient abstraction of-velocity energy.Also, due to flow disturbance in the moving blade passages, inconsequence of such departures of the angle of approach, the reactionaction would be less eiiicient. Abstraction of energy by the movingblades in both of these ways may be Iimproved, where the angle ofapproach of elastic fluid varies, by using blades of foil section havingwell-rounded inlet edges. If such blades are used, irrespective ofwhether the action is impulse or reaction, improved performance both ofthe stationary and the moving blades is secured where the velocity ofapproach is subacoustic. Hence, with like stationary and moving bladesforming a stage, the more predominant velocity abstraction,-characte'ristic of the usual Rateau stage, may be secured by gauging sothat greater enthalpy change occurs in the stationary blade passagesthan in the moving blade passages, and the comparatively greaterreaction effect, characteristic of the ordinary re-r action or Parsonsstage, may be secured bygauging of the blades so that the enthalpychanges both in the stationary and in the moving blade passages aresubstantially the same. Thus, for sub-acoustic velocities, the same foilsection may be used both for the stationary and moving blades,thedesired distribution of enthalpy change thereover being secured byappropriate choice of orientation and pitch of the blades. Therefore, inaccordance with thepresent invention, I provide a turbine having stagesfor elastic fluid approaching both the stationary and I moving bladesthereof at sub-acoustic velocities and both the stationary and movingblades being of foil section with well-rounded inlet edges;

and, without changing the foil and shape, the distribution of enthalpychange between the stationary and moving blades of a stage is attainedthrough variation of the pitch and orientation of the blades of therespective rows.

A further object of the invention is to provide lan' elastic-fluidturbine wherein the blades or vanes subject to super-acoustic velocityhave sharp' or thin leading edges and the blades or vanes subject tosub-acoustic velocity are of foil section having well-rounded inlet orleading edges.

A further object of the invention is to provide turbine bladingincluding an initial multiple-velocity-abstraction impulse stage whereinthe rst row of moving blades thereof have sharp or thin leading edgesand the second row of moving blades are of foil section and haveWell-rounded inlet or leading edges.

A further object of the invention is to provide a turbine havingsingle-velocity-abstractian impulse stages for sub-acoustic velocityelastic fluid and wherein both the stationary and moving blades of eachstage are of foil section and have well-rounded inlet or leading edges,the distribution of enthalpy change over the stationary and movingblades of each stage being secured by variation of the pitch andorientation of the blades in the row without any changes in thefoilshape.

These vand other objects are effected by my invention as will beapparent from the following description and claims taken inconnectionwith the accompanying drawings forming a part of this application, inwhich:

Fig. 1 is a diagrammatic view showing a multiple-velocity-abstractionstage-having the iirst row of moving blades thereof suitable forsuperacoustic velocities and the last row of moving bladesl thereofmodified for elastic fluid entering at sub-acoustic velocity;

Fig. 2 is a view similar to Fig. l but showing modification of thenozzles and the iirst row of moving blades as Well as of theintermediate reversing blades;

Fig. 3 is a side elevational view of a turbine sectioned to show stagesthereof;

Fig. 4 is a detail sectional view 'of stages of the turbine shown inFig. 3; Figs. 5 'and 6 are sectional views showingpartial-peripheral-admission and full-peripheral admission diaphragms ofthe' turbine shown in Fig. 3:

Fig. 7 is a sectional view showing a multiplevelocity-abstraction stagefollowed by stages of the type wherein the distribution of enthalpychange over the stationary and moving blades is uniform; x

Figs. 8 and 9 are detail views of 4blade elements suitable for receivingelastic iluid at sub-acoustic Velocity;

Figs. 10, 11 and 12 are diagrammatic views explanatory of principlesinvolved.

The multiple-velocity-abstraction stage, at I0, has the customary nozzlegroup or groups including vane elements I4 defining nozzle passages I5,a first row of moving blades I6, an intermediate row of stationaryreversing blades I1, and a second row of moving blades I8.

As elastic fluid issues from the nozzle passages l5 at super-acousticvelocity, the rst row of moving blades I6 have sharp leading or inletedges I9 in order to minimize the projected area presented to theapproaching stream so as to reduce energy losses due to compressionshocks.

If elastic uid approaches the intermediate reversing blades I1 atsuper-acoustic velocity, then these blades should also have thin orsharp leading edges. Due to abstraction of velocity energy from theelastic uid by the first row of moving blades I6 and to inherent lossesboth in the blades I6 and I'I, the elastic fluid usually-approaches thebladesy I8 of the second row at a sub-acoustic velocity and the bladesshould, for that reason, be of foil section and have Wellrounded inletor leading edges.

Impulse blades of the sharp-edge type should have a total geometricalturning angle equal to that required of the fluid at design operationconditions. On the other hand, with sub-acoustic velocities of approachof elastic iluid, this is Y immaterial for blades of foil section andhaving well-rounded inlet edges.

Preferably, as shown in Fig. 2, the iirst moving row of impulse bladesISa, in addition to presenting sharp inlet edges I9, have concave faces20 and polygonal convex faces 2| defining Prandtl-Meyer streamline owpassages 22 for elastic iiuid entering at super-sonic velocity, asdisclosed and claimed in the application of Stewart Way, Serial No.335,465, led May 16, 1940, and assigned to the Westinghouse Electric &Manufacturing Company. Each convex face 2i includes a pluralityr of fiatportions 23 joined by corner portions 24, the corner portions functionto induce turning of the stream in each passage under the conditionsprovided by the concave face. As pointed out in said application, theadvantage for this type of passage is to minimize shock loss. l

Fig. 2 also shows vane elements Ia. dening nozzle passages Ia of highexpansion ratio, the vane/elements being constructed and arranged toprovide for pressure-velocity conversion and the turning of the jet ineach passage with expansion to a super-acoustic velocity with minimumenergy losses. Each of the vanes has a corner 25 to produce the newaround a corner effect in each -passage in turning the jet in thelatter. The vane elements have Well-rounded inlet edges 26, thin'exitedges 21 and the corners 25. From the inlet edges, the foils havesubstantially fiat ,surfaces 28y and 29 which converge inwardly to thethroat sections defined by the corners and the opposed fiat surfaces 29.Beyond the throat approach. As changes in load or turbine speed or bothcause the angle of approach to vary, the

capacity of the rounded inlet edges to bring.

about the automatic accommodation of Athe stream to suit the bladeprofiles with minimum energy losses is important. This will be clearfrom a consideration of Figs. and 11.

In Figrl, the stream approaches in the direction a relatively to theblades b of streamlined section and having Well-rounded inlet edges c.v

region d in such a manner as to cause the streamlines to accommodatethemselves to the blade section.' This action induced by thewell-rounded inlet edges results in a now condition similar to a sharpedge or lip extending from the forward side ofthe blade in the directionof approach of the stream. If the direction of approach changes from aof Fig. 10 to a' of Fig. 11, the bladey sections in these views beingidentical in all respects, it will be obvious that a sharp edge or lipcorrect for the direction a would be is, the sharp edge or lip, for goodefliciency, is

critical to the angle of approach. On the other hand, the streamlinedsection with a well-rounded inlet edge operates with good efficiencyover a wide range of variation in the angle of approach.

The diierence in efliciency of the sharp edge blade as compared with thefoil section with a well-rounded inlet edge is shown in Fig. 12, wherethe curve e is the efficiency curve for a sharp-edged blade and thecurve f is that for a streamlined section with a well-rounded inletedge. The top or peak portion of the curve ,f

is much flatter than e showing that good effi-f ciency is had over awide velocity ratio range, and, as the direction of approach changeswith changes invelocity ratio, good emciency is maintained withvariation of the angleof approach over a wide range. Hence, in Fig. 11,even though the direction of approach a is substantially different froma in Fig. 10, the action is the same, that is, the well-rounded inletedge sets up a disturbance which is propagated backwardly into thestream and causes the latter to accommodate itself to the blade section.f

The gauging, or ratio of opening o to the pitch s (all Fig. 9), of thestationary vane elements may be equal to or less than that of thecooperating moving vaneA elements. If the ratios are equal, then thestage is symmetrical with respect i to the distribution pf enthalpychange over the As the velocity of approach is sub-acoustic, the

well-rounded inlet edges c propagate disturbancesbackwardly into thestream in the general stationary and moving vane elements. On the otherhand, if the ratio for the stationary vane elements of a stage issmaller than that for the moving vane elements thereof, then the stageis anti-symmetrical with respect to distribution of enthalpy change overthe vane elements, that is, the proportion of kinetic energy generatedin the nozzle passages of the stationaryvane elements becomes larger, assaid ratio for the 'stationary vane elements is made smaller.

If the elastic fluid approaches the intermediate stationary or reversingblades ofthe initial multiple-veiocity-abstraction stage at sub-sonic.velocity, then such blades, as shown at I'I'a in Figs. 2 and 7, shouldbe of foil'section having well-rounded inlet edges. Blades of foilsection with well-rounded in Vlet edges should not be used withvelocities of an initial multiple-velocity-abstraction stage, at

IIJ, followed by single-velocity-abstraction stages, at II and I2. Eachsingle-velocity-abstraction stage, at il, comprises a diaphragm 32having arcuate groups or vane elements 33 providing nozzle passages 3Efor delivering elastic fluid to the moving bladel or vane elements 35carried by the disk 36, the diaphragm and the disk such root portionsfastened in-a groove, the desired orientation and pitch of the bladeportions 38 will be had.

For the same blade width, the dimensions of the streamlined or foilsection may vary substantially; however, in all cases, the inlet edgeshould be well-rounded, that is, its radius of curvature should besubstantial in relation to the maximum section thickness. As shown, thethickness, or diametral dimension, of the inlet edge at the point wherethe concave face surface joins the convex inlet edge surface, the pointof reverse curvature, is equal to at least the major portion ofthemaximum thickness ol the section, or, stated another way, the radius ofthe inlet edge should not' be greater than half the maximum thickness ofthe section and not less than onequarter thereof.

'I'he term enthalp y" as used herein, has the sense of a thermodynamicconception o1' derived quantity. It has the signicance of heat drop inthe Molliere diagram. See page 47, chapter 3, of Notes onThermodynamics, third edition, Dr. John A. Goii', published by John S.Swift Company, Inc., St. Louis, 1939.

While I havel shown my invention in several forms, it will be obvious tothose skilled in the art that it is not so limited, but is susceptibleof various other changes and modifications without departing from thespirit thereof, and I desire, therefore, that only such limitationsshall be placed thereupon as aref specically set forth in the appendedclaims.

What I claim is:

1. In an elastic-huid turbine, a plurality of stages, each includingstationary and moving rows of blades, the initial stage including meansfor converting heat energy of elastic uid into velocity energy such thatelastic iluid is supplied to blades thereof at super-acoustic velocity,the first row of blades of the initial stage receiving elastic fluid at'super-acoustic velocity having sharp inlet edges, and the remainingblades each being of foil section and having well-rounded inlet edges sothat those bladeswhich encounter a sub-acoustic inlet velocity canaccommodate a accommodate themselves to the blade over a wide range ofvariation in the angle of approach of the elastic iluid; and said otherstages including stationary and moving blades each of foil section andhaving an inlet edge suiiiciently wellrounded to cause streamlines ofelastic iluid approaching at sub-acoustic velocity to accommodatethemselves to the blade over a-wide range of variation in the angle ofapproach of the elasticfluid.

V4. In an elastic fluid turbine, a multiple-velocity-abstraction stageincluding a iirst row of moving blades having sharp inlet edges, asecond row of moving bladesrof foil section and having inlet edgessufficiently well-rounded to cause the streamlines of elastic fluidapproaching at sub-acoustic velocity to accommodate themselves to theblades over a wide range of variawide range of variation in the angle ofapproach of the elastic iiuid.

2. In an elastic-fluid turbine, alternately-arranged stationary andmoving rows of blades,

A nozzles for supplying elastic fluid at super-acoustic velocity to therst row of moving blades, the blades receiving elastic' uid atsuper-acoustic velocity having sharp inlet edges and the remainingblades receiving elastic uid at s ubacoustic velocities each being offoil section with an inlet edge sufliciently well-rounded to cause thestreamlines of elastic iiuid approaching at sub-acoustic velocity toaccommodate themselves to the blade over a wide range of variation inthe angleof approach.

3. In an elastic uid turbine, a plurality of stages for progressivelyabstracting energy from elastic iiuid and comprising an initial stageand a plurality of other stages; said initial stage in- /cluding rst andsecond rows of moving blades.

f a row of stationary reversing blades arranged between the rst andsecond rows oi.' moving blades, and nozzles for supplying elastic iiuidat superacoustic velocity to the rst row of moving blades, the blades ofsaid first moving row having sharp inlet edges and those of said secondmoving row each being of foil section and having -an inlet edgesum'ciently well-'roundedv to cause the streamlines of approachingelastic fluid to tion in the angle of approach of elastic iluld,intervening reversing blades, and nozzles for supplying elastic iiuid atsuper-acoustic velocity tc the first row of moving blades.

5. In an elastic-fluid turbine, a multiple-velocity-abstraction stageincluding a first row of moving blades having sharp inlet edges, asecond row of moving blades, stationary reversing blades between thefirst and second rows of moving blades. said stationary reversing bladesand said second row of moving blades each `being of foil section with aninlet' edge sufciently well-rounded to cause streamlines of elasticfluid approaching at sub-acoustic velocity to accommodate themselves tothe blade over a wide range of Variation in the angle of approach ofelastic uid, and nozzles for supplying elastic iiuid at super-acousticvelocity to the first row of moving blades.

6. In an elastic-fluid turbine, a stage for abstracting energy fromelastic fluid delivered thereto at sub-acoustic velocity, said stagecomprising a row of stationary vanes delivering elastic uid tov a row ofmoving vanes, said stationary and 'moving vanes each being ofstreamlined foil section and having an inlet edge sumciently wellroundedto cause streamlines of elastic uid approaching at sub-acoustic velocityto accommodate themselves to the vane over a wide Arange of variation inthe angle of approach of elastic fluid and the ratio of opening to pitchfor the stationary vanes being smaller than that for the moving vanes inorder to provide for greater' enthalpy change in the former than in thelatter.

7. In an elastic-Huid turbine, a plurality of' stages including aplurality of single-velocityabstraction stages, eachsingle-velocity-abstraction stage comprising a stationary row of vaneelements and a moving row of vane elements, both the stationary and themoving vane elements being of streamlined foil section and having aninlet edge. suillciently well-rounded t0 cause streamlines of elasticfluid approaching at sub-acoustic velocity to accommodate themselves tothe vane element over a wide range of.

variationin the angle of approach of elastic fluid and the ratio ofopening to pitch for the station- -ary vane elements being smaller thanthat for the moving vane elements in orderi-provide for greater enthalpychange in thea'ormeir `than in -the latter. V e f 8. In an elastic-fluidturbine, a plurality of stages including a multiplicity ofsingle-velocity- Aabstraction stages, thel single-velocity-abstractionstages including partial-peripheral admission and full-peripheraladmission stages each comprising stationary and moving vanes, each ofsaid vanes being of streamlined foil section and having an inlet edgesufciently well-roundedtoI cause streamlines of elasticl iluidapproaching at sub-acoustic velocity to accommodate themselves to thevane over a wide range of variation in the angle of approach of elasticuid and the ratio of opening to pitch for the stationary vanes beingsmaller than that for the moving vanes in order to provide for greaterenthalpy change in the former than in the latter.

9. In an elastic-fluid turbine, a plurality of stages inclu/ding aplurality of single-velocity-abstraction stages, eachsingle-velocity-abstraction stage comprising a casing diaphragm, a rotordisk, stationary vane elements carried by the dlaphragm and providingnozzle passages, moving vane elements carried by the disk and providingpassages for elastic fluid delivered by the nozzle passages, boththelstationary and the moving vane elements being of streamlined foilsection with an inlet edge suiciently well-rounded to cause streamlinesof approaching elastic fluid to accommodate themselves to the vaneelements over a wide range of variation in thevangle of approach ofelastic fluid and the ratio of opening to pitch for the stationary vaneelements being smaller than that for the moving vane elements in orderto provide for greater enthalpy change in the former than in the latter.

l0. In an elastic-fluid turbine, an initialmultiple-velocity-abstraction stage followed by a plurality ofsingle-velocity-abstraction stages;

each single-velocity-abstraction stage comprising a casing diaphragm, arotor disk, stationary vane elements carried by the diaphragm andproviding nozzle passages, and a moving row of vane elements carried bythe disk and providing passages for elastic iluid delivered by thenozzle passages, both the stationary` and the moving vane elements eachbeing of streamlined foil section and having an inlet edge sulcientlywellrounded to cause streamlines of elastic :duid approaching atsub-sonic velocity to accommodate themselves to the vane element over aWide range of variation in the angle of approach of elastic uid and theratio of opening to pitch for the stationary vane elements being smallerthan that for the moving vane elements in order to provide for greaterenthalpy change in the former than in the latter.

11. In an elastic-iiuid turbine, an initial multiple-velocty-abstractionstage followed by a plurality of single-velocity-abstraction stages themultiple-velocity-abstraction stage comprising iirst and second rows ofmoving vane elements, an intervening row of reversing vane elements andnozzles for delivering elastic fluid at super-acoustic velocity to theilrst row of moving vane elements; each single-velocity-abstractionstage comprising stationary vane elements providing nozzle passages, arow of moving .vane elements providing passages for elastic fluiddelivered by the nozzle passages; the rst row of moving vane elements ofthe multple-velocity-abstraction stage having sharp inlet edges and thesecond row of moving vane elements thereof and both the stationary andmoving vane elements of each of the single-velocity-abstractionistageseach being of streamlined foil section and having an inlet edgesuiciently well-rounded to cause streamlines of elastic iluidapproaching at sub-acoustic velocity to accommodate themselves to thevane element over a wide range of variation in the angle of approach ofelastic fluid and the ratio of opening to pitch for the stationary vaneelements of the single-velocity-abstraction stages being smaller thanthat for the moving vane elements thereof in order to provide forgreater enthalpy change in the former than in the latter.

WINSTON RANDOLPH NEW.

